1. Technical Field
The disclosure relates to an encapsulation of illumination photosensitive device. Particularly, the disclosure relates to an encapsulation of backside illumination photosensitive device.
2. Related Art
Along with popularity of multimedia, digital image devices are developed in succession, and an illumination photosensitive device serving as a critical component thereof becomes increasingly important. The illumination photosensitive device is mainly in charge of converting image into electrical signals, and the illumination photosensitive devices generally include charge coupled devices (CCD) and complementary metal oxide semiconductor (CMOS) photosensitive devices, etc.
FIG. 1A is a cross-sectional view of a conventional encapsulation of front illumination photosensitive device. FIG. 1B is a cross-sectional view of a conventional encapsulation of backside illumination photosensitive device (which is also referred to as an encapsulation of backside illuminated type photosensitive device). Referring to FIG. 1A, in the encapsulation of front illumination photosensitive device 100A, an interconnection layer 120 is disposed on a light receiving surface S1 of a photosensitive device array 110, and an optical micro-structure layer 140 and a color filter layer 130 are disposed on the interconnection layer 120. Therefore, besides passing through the optical micro-structure layer 140 and the color filter layer 130, a light beam L has to further pass through the interconnection layer 120 before being received by the photosensitive device array 110. Since metal layers 122 in the interconnection layer 120 may reflect the light beam L to decrease an intensity of the light sensed by the photosensitive device array 110, the conventional encapsulation of front illumination photosensitive device 100A has disadvantages of a low fill factor (which is referred to a ratio between an area in a single pixel capable of receiving the light beam and the whole pixel area) and a low contrast, etc.
Therefore, the encapsulation of backside illumination photosensitive device 100B (shown in FIG. 1B) is provided, in which the interconnection layer 120 is disposed on a back surface S2 (opposite to the light receiving surface S1) of the photosensitive device array 110, and the optical micro-structure layer 140 and the color filter layer 130 are disposed on the light receiving surface S1 of the photosensitive device array 110. Therefore, the light beam L does not pass through the interconnection layer 120 before the light beam L is received by the photosensitive device array 110. In this way, the light beam L is avoided to be reflected by the interconnection layer 120, so as to improve the fill factor and contrast of the encapsulation of backside illumination photosensitive device 100B.
However, the interconnection layer 120 located on the back surface S2 of the encapsulation of backside illumination photosensitive device 100B is generally required to connect with a circuit substrate (not shown). Since the circuit substrate has a poor thermal conductivity, the encapsulation of backside illumination photosensitive device 100B cannot efficiently dissipate heat and leakage current is generated. Accordingly, problems of poor sensitivity, signal interference and uneven imaging are generated.